Hi, tiredness is a recognised potential side effect when taking Cymbalta. If this is a new medication for you, it may improve, but some people are affected longer term. If this is the case, and is affecting your day to day living, you should have a discussion with your doctor... Check out the link below for a full list of potential side effectshttps://www.drugs.com/sfx/cymbalta-side-effects.html

I was on Cymbalta for 3 years. side affects I encountered were, bad hot flashes /sweating, no periods, and lack of libido. Other than that it worked on depression and pain great. This does not mean you will experience any of these, you may not have any, or even different ones, everyone reacts differently as you know. Hope this helped